Electronic structure of alpha and gamma phases of Si(111)-R3xR3-Sn
Abstract
This work presents a detailed comparison of the electronic properties of two phases a and g. of the prototypical
Si111.–'3 ='3 –Sn system, focussing on the empty surface states. The latter reconstruction has been studied at room
temperature with inverse photoemission KRIPES.. For the g-phase characterised by an equal amount of Sn and Si adatoms,
a charge transfer towards the Sn adatom leaves an empty surface state localised on Si adatoms, and observed in KRIPES 0.4
eV above the Fermi level EF. at the surface Brillouin zone SBZ. center. The band gap of this semiconducting g-phase is
estimated around 0.5 eV. In contrast, the a phase with only Sn adatoms shows a metallic behaviour and two distinct
adatom-derived empty surface states.